Microwave Spectra, Structure, and Electric Dipole Moment of the Ar-Isocyanic Acid van der Waals Complex

Autor: C W. Gillies, J Z. Gillies, Christopher W. Boyce, R D. Suenram, H. E. Warner, F. J. Lovas
Rok vydání: 1995
Předmět:
Zdroj: Journal of Molecular Spectroscopy. 171:533-545
ISSN: 0022-2852
DOI: 10.1006/jmsp.1995.1140
Popis: The microwave spectra of Ar-HNCO and Ar-DNCO have been investigated with a pulsed-nozzle Fourier-transform microwave spectrometer in the region of 8 to 18 GHz. One state is observed for each isotopomer and the a- and b-type transitions are fitted to an asymmetric top Hamiltonian. The spectral constants obtained from this fit for Ar-HNCO are A = 11224.5667(9) MHz, B = 1937.6357(5) MHz, C = 1638.6608(2) MHz, ΔJ = 14.689(10) kHz, ΔJK = 388.52(13) kHz, ΔK = −313.85(37) kHz, δJ = 2.471(2) kHz, χaa = −0.946(3) MHz, and χbb = 2.024(4) MHz. Stark effect measurements determine μa = 1.3940(50) × 10−30 C m [0.4179(15) D] and μb = 5.1219(83) × 10−30 C m [1.5355(25) D] for Ar-HNCO. The inertial defects, Δ in uA2, are 2.5629 and 2.555 for Ar-HNCO and Ar-DCNO, respectively. A planar T-shaped structure is determined from the effective moments of inertia with an Ar to HNCO center-of-mass separation of 3.577 A. The moment of inertia data indicate that the oxygen is tilted toward the argon and the hydrogen is oriented syn with respect to argon. However, the small measured value of μa in the complex compared to μb in the monomer, HNCO, suggests that the hydrogen undergoes internal rotation approximately about the heavy atom axis of HNCO (a inertia axis of HNCO) which would mean the effective moments of inertia are averaged over this motion. Comparison of the quadrupole coupling constants in HNCO to Ar-HNCO also provides evidence in support of this internal motion. The uncertainties shown in parentheses are one standard deviation.
Databáze: OpenAIRE
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